The goal of this work is to establish Magnetic Resonance Imaging (MRI) as a reliable and sensitive noninvasive diagnostic test for mesenteric ischemia. This would allow for earlier diagnosis than is currently possible using existing procedures and decreased morbidity and mortality in the acute form of the disease, and for more accurate diagnosis of the chronic form for increased success of surgical treatment. To achieve this goal, To this end, the specific aims of this work would include: 1. To prove that flow-independent T2 measurements with MR would provide accurate measurements of blood oxygen saturation in the superior mesenteric vein (SMV); 2. To prove that a threshold level of blood flow which oxygen uptake decreases can be demonstrated noninvasively by simultaneous MR measurements of superior mesenteric artery (SMA) blood flow and blood oxygen saturation in SMV using a canine model; 3. To establish the normal range of SMA blood flow and SMV blood oxygen saturation in health volunteers; 4. To correlate MR SMA blood flow, SMV blood oxygen saturation measurements and oxygen parameters with pathologic changes in canine models, and to develop a grading scale using MR parameters which can be used reliably to predict ischemic pathologic changes in the bowel; 5. To prove that accurate diagnosis of acute extensive mesenteric ischemia in patients can be made with MR. Surgical pathology and clinical outcome would be used as the gold standard; and 6. To prove that accurate diagnosis of chronic mesenteric ischemia in patients can be made with MR. Surgical pathology and clinical outcome would be used as the gold standard.